This invention relates generally to improvements in radius bending dies of the type used in tube bending machines for bending metal tubing or the like to a selected configuration, wherein such bent tubing may be used, for example, in vehicular exhaust and tailpipe systems, etc. More particularly, this invention relates to an improved bending die that is detachably secured within a novel ram assembly which enables the bending die to be mounted onto the tube bending machine in an efficient, drop-in manner that allows various sized bending dies to be interchanged without the use of accessory tools.
Tube bending machines in general are relatively well known in the art for use in bending metal tubing to a selected configuration. Such tube bending machines are commonly used by automotive vehicle repair shops to shape a length of metal tubing in a customized fashion for use in a vehicle exhaust or tailpipe system. A typical tube bending machine includes a bending die carried by a hydraulic ram for advancement into bending engagement with a length of metal tubing supported by a pair of backshoe dies mounted respectively on an outwardly pivoting pair of back gates. The bending die has a convexly curved, typically semicircularly shaped bending die face which cooperates with complementary die faces of the backshoe dies to define a channel of generally circular cross section having a diametric size closely matching the size of metal tube being bent by the machine. The bending die is advanced along a line extending between the pivot axes of the back gates and pushes into the supported metal tube, thereby causing the back gates with their backshoe dies to react by pivoting outwardly in unison and in opposite directions away from the bending die. This combination of bending die and back gate pivoting motion cooperates to bend the metal tube through a selected angle, in accordance with the advancement stroke length of the bending die.
One commercial example of a tube bending machine of this general type is marketed under the trademark BLUE BOY, by American Machine & Hydraulics, Inc., of Newbury Park, Calif. See also U.S. Pat. No. 3,388,574.
A major problem previously associated with mounting the bending die arises from the need to interchange bending dies of different radius of curvature in order to bend tubing into a desired configuration. Many prior bending dies cannot be rapidly detached and substituted by a different, appropriately sized die. Another general problem encountered with use of bending dies occurs during retraction of the bending die from the bent tubing, when tubing engagement forces and/or slight tubing compression can cause the bending die to stick or hang up on the tubing. Positive mechanical retraction of the bending die is needed for these reasons, but prior mechanical arrangements for positive retraction have been incompatible with simple die changeover.
In one common bending die mounting configuration, the bending die includes two rearwardly extending pins for sliding reception into open bores in a pusher block carried by the hydraulic ram. A mechanical stop is interlocked with at least one of the pins so that when the pusher block is retracted, the mechanical stop is engaged by the pusher block to retract the bending die. In this attachment arrangement, bending die removal is prohibited unless the mechanical stop is first removed. Accordingly, manipulative steps often requiring the use of tools are required to change bending dies. Moreover, removal of parts such as mechanical stops can result in the parts being misplaced or lost, causing further delays in machine operation.
Other prior mounting configurations have been designed to permit faster changeover of the bending die. For example, the pusher block has been provided with a hinged mechanical clamp or with upstanding pins to interlock with an appropriately apertured bending die, to permit bending die installation or removal without separate mechanical retractor stops. However, such past solutions generally have been less than ideal.
There exists, therefore, a significant need for an improved bending die which can be mounted onto the pusher block in a manner that permits the bending die to be easily and quickly changed without tools or accessory parts, wherein the bending die incorporates means for physically retracting the bending die from bent tubing at the conclusion of a bending step. The present invention fulfills these needs and provides further related advantages.